90 lines
2.4 KiB
C++
90 lines
2.4 KiB
C++
/*
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Copyright (c) 2013 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include <unordered_set>
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#include <vector>
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#include "expr.h"
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namespace lean {
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class max_sharing_functor {
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struct expr_struct_eq { unsigned operator()(expr const & e1, expr const & e2) const { return e1 == e2; }};
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typedef typename std::unordered_set<expr, expr_hash, expr_struct_eq> expr_cache;
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expr_cache m_cache;
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void cache(expr const & a) {
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a.raw()->set_max_shared();
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m_cache.insert(a);
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}
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public:
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expr apply(expr const & a) {
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auto r = m_cache.find(a);
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if (r != m_cache.end()) {
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lean_assert((*r).raw()->max_shared());
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return *r;
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}
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if (a.raw()->max_shared()) {
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m_cache.insert(a);
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return a;
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}
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switch (a.kind()) {
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case expr_kind::Var: case expr_kind::Constant: case expr_kind::Prop: case expr_kind::Type: case expr_kind::Numeral:
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cache(a);
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return a;
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case expr_kind::App: {
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std::vector<expr> new_args;
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bool modified = false;
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for (expr const & old_arg : args(a)) {
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new_args.push_back(apply(old_arg));
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if (!eqp(old_arg, new_args.back()))
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modified = true;
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}
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if (!modified) {
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cache(a);
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return a;
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}
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else {
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expr r = app(new_args.size(), new_args.data());
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cache(r);
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return r;
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}
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}
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case expr_kind::Lambda:
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case expr_kind::Pi: {
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expr const & old_t = abst_type(a);
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expr const & old_b = abst_body(a);
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expr t = apply(old_t);
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expr b = apply(old_b);
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if (!eqp(t, old_t) || !eqp(b, old_b)) {
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name const & n = abst_name(a);
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expr r = is_pi(a) ? pi(n, t, b) : lambda(n, t, b);
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cache(r);
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return r;
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}
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else {
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cache(a);
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return a;
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}
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}}
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lean_unreachable();
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return a;
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}
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};
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expr max_sharing(expr const & a) {
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if (a.raw()->max_shared()) {
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return a;
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}
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else {
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max_sharing_functor f;
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return f.apply(a);
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}
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}
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} // namespace lean
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